Phosphorous-Based Sensors For Detection Of Multiple Solvents

ABSTRACT

Embodiments of the present disclosure pertain to methods of monitoring an environment for the presence of a solvent by: (i) exposing the environment to a luminescent compound, where the relative luminescence emission intensity of the luminescent compound changes upon interaction with the solvent; and (ii) monitoring a change in the relative luminescence emission intensity of the luminescent compound, where the absence of the change indicates the absence of the solvent from the environment, and where the presence of the change indicates the presence of the solvent in the environment. The luminescent compounds include a phosphorous atom with one or more carboxyl groups, where the carboxyl groups are coordinated with one or more metallic ions (e.g., lanthanide ions and yttrium ions). The present disclosure also pertains to sensors for monitoring an environment for the presence of a solvent, where the sensors include one or more of the aforementioned luminescent compounds.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 16/991,147, filed on Aug. 12, 2020, which is a continuationapplication of U.S. patent application Ser. No. 15/572,411, filed onNov. 7, 2017, which is a U.S. national stage application ofPCT/US2016/031593, filed on May 10, 2016, which claims priority to U.S.Provisional Patent Application No. 62/159,602, filed on May 11, 2015;and U.S. Provisional Patent Application No. 62/281,830, filed on Jan.22, 2016. The entirety of each of the aforementioned applications isincorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

This invention was made with government support under Grant no.DMR1506694 awarded by National Science Foundation. The government hascertain rights in the invention.

BACKGROUND

Current methods and sensors for detecting solvents in variousenvironments have numerous limitations, including limitations in termsof speed, efficiency, accuracy, and reproducibility. For instance,current methods of detecting solvents within solvent feed stocks requiresample isolation and chemical analysis. The present disclosure addressessuch limitations.

SUMMARY

In some embodiments, the present disclosure pertains to methods ofmonitoring an environment for the presence of a solvent. In someembodiments, the methods include: (i) exposing the environment to aluminescent compound, where the relative luminescence emission intensityof the luminescent compound changes upon interaction with the solvent;and (ii) monitoring a change in the relative luminescence emissionintensity of the luminescent compound, where the absence of the changeindicates the absence of the solvent from the environment, and where thepresence of the change indicates the presence of the solvent in theenvironment.

The luminescent compounds of the present disclosure include aphosphorous atom with one or more carboxyl groups, where the carboxylgroups are coordinated with one or more metallic ions. In someembodiments, the metallic ions include, without limitation, lanthanideions, yttrium ions, and combinations thereof. In some embodiments, thephosphorous atom in the luminescent compound is oxidized. In someembodiments, the luminescent compound is porous. In some embodiments,the luminescent compound is in the form of a crystalline lattice, wherethe metallic ions in the luminescent compound coordinate with carboxylgroups on adjacent luminescent compounds to form the crystallinelattice.

In some embodiments, the environment is a liquid environment, such asreservoirs, water formations, solutions, solvent feed stocks, andcombinations thereof. In some embodiments, the solvent to be detected inthe environment includes, without limitation, water, alcohols, dioxane,toluene, dimethyl formamide, hexanes, chloroform, acetonitrile,pyridine, deuterium oxide, and combinations thereof.

In some embodiments, environments are exposed to a luminescent compoundby methods that include, without limitation, mixing, incubating,swapping, dipping, and combinations thereof. In some embodiments, thechange in the relative luminescence emission intensity of theluminescent compound occurs when the solvent in the environmentreversibly penetrates the luminescent compound. In some embodiments, thechange in the relative luminescence emission intensity of theluminescent compound is represented by a change in color, a change invisible light emission intensity, a change in visible light emissionpattern, and combinations thereof.

In some embodiments, the change in the relative luminescence emissionintensity of the luminescent compound is monitored visually, inreal-time, by utilization of a spectrometer, or by combinations of suchmethods. In some embodiments, a single luminescent compound is utilizedto monitor the presence of a plurality of different solvents in theenvironment, where each of the plurality of different solvents causes adistinguishable change in the relative luminescence emission intensityof the luminescent compound. In some embodiments, a plurality ofdifferent luminescent compounds are utilized to monitor the presence ofone or more solvents in the environment.

In additional embodiments, the present disclosure pertains to sensorsfor monitoring an environment for the presence of a solvent. In someembodiments, the sensors include one or more luminescent compounds ofthe present disclosure.

FIGURES

FIG. 1 provides a scheme of a method of monitoring an environment forthe presence of a solvent.

FIG. 2A, FIG. 2B, FIG. 2C, FIG. 2D, and FIG. 2E provide variousillustrations of phosphine coordination material 22 (PCM-22), includingthe nodal connectivity in PCM-22 (FIG. 2A); space-filling view of PCM-22along the c-axis showing 1D hexagonal channels (FIG. 2B); space-fillingview perpendicular to channel direction, showing close-stacking ofadjacent sheets (alternate sheets shown in green for clarity) (FIG. 2C);3,3,-connected net version of FIG. 2C (FIG. 2D), where P=pink andTb=blue); and the closest inter-layer O—H interactions (dashed greenbonds) (FIG. 2E).

FIG. 3 shows the carbon dioxide (CO₂) adsorption of PCM-22 activated atvarious temperatures.

FIG. 4 shows the CO₂ BET surface area (p=1.0 atm) of PCM-22 whenactivated at various temperatures.

FIG. 5 shows the thermogravimetric analysis of as-synthesized andactivated PCM-22. TGA was measured under N₂ carrier gas.

FIG. 6 shows the emission spectrum (⁵D4 to ⁷FJ) of Tb-PCM-22.

FIG. 7 shows the orientation of 1,4-dioxane molecules within the poresof as-synthesized PCM-22. The green dashed bonds show the shortestdioxane-O..HOH contacts (2.05 Å).

FIG. 8A and FIG. 8B show the ³¹P{¹H} NMR spectra of various PCM-22compounds, including the ³¹P{¹H} NMR spectra of static Tb-PCM-22 showingspin-mapping experiments at various carrier frequencies (FIG. 8A, 1000ppm (bottom), 1000 ppm (next) and 0 ppm (next); Top: a sum of theprevious three spectra); and the ³¹P{¹H} NMR spectra of Tb—O=PCM (FIG.8B, obtained in a sample spinning at 12 kHz (top), 10 kHz (next) and 13kHz (bottom)).

FIG. 9 shows a Fourier transform infrared spectroscopy (FT-IR) of PCM-22(green, top) and O=PCM-22 (black, bottom).

FIG. 10 shows a comparison of single crystal structures before and afteroxidation at P. The top image shows a view of one P center. The bottomimage shows a comparative view of packing, perpendicular to the plane ofthe sheets.

FIG. 11 shows a powder x-ray diffraction (PXRD) of PCM-22 and O=PCM-22compared to the simulated powder pattern.

FIG. 12 shows a comparison of CO₂ adsorption-desorption isotherms forPCM-22 and O=PCM-22.

FIG. 13 shows a comparison of normalized emission spectra for PCM-22 andO=PCM-22.

FIG. 14A and FIG. 14B show various data relating to PCM-22 and O=PCM-22.FIG. 14A shows PXRD patterns for PCM-22 and O=PCM-22 as a function ofsolvation state (black=simulated data; red=as-synthesized;green=activated; yellow=re-solvated, 5 min; blue=resolvated, 10 days).FIG. 14B shows corresponding average ϕ_(PL) values for PCM-22 (green)and O=PCM-22 (red).

FIG. 15 shows temperature-dependent PXRD patterns for PCM-22 (leftpanel) and O=PCM-22 (right panel) as a function of activationtemperature (bottom to top: simulated data (orange); 298 K (blue); 323 K(red); 348 K (green); 373 K (purple); when cooled back to 298 K (cyan)).

FIG. 16 shows temperature-dependent FT-IR data showing loss of H₂Ostretching bands in PCM-22 upon activation.

FIG. 17A, FIG. 17B, FIG. 17C, and FIG. 17D show light micrograph imagesof PCM-22 crystals taken over 10 days, showing no new nucleation ordissolution. The images were taken at the initial stage of nucleation(FIG. 17A); 1 day after nucleation (FIG. 17B); 5 days after nucleation(FIG. 17C); and 10 days after nucleation (FIG. 17D).

FIG. 18 shows response time study and reversibility of luminescenceturn-on-turn-off for PCM-22 (green) and O=PCM-22 (red). The averageemission intensities are shown as solid lines with shaded areas showingthe error range obtained from three independent experiments. The insetshows excited state lifetimes.

FIG. 19A, FIG. 19B, and FIG. 19C provide images of various PCM-22materials before and after exposure to solvents. FIG. 19A show images oflight emission from PCM-22 materials that include Tb, Eu and mixedTb:Eu. FIG. 19B shows the colors observed when the 1:1 Tb:Eu PCM-22(originally yellow, as shown in FIG. 19A) is exposed to hexanes (red),dimethyl formamide (bright yellow), chloroform (orange), water (green),and heavy water (non-emissive). FIG. 19C shows a wider variety of colorsobserved for Tb:Eu:Tm trimetallic versions of PCM-22.

DETAILED DESCRIPTION

It is to be understood that both the foregoing general description andthe following detailed description are illustrative and explanatory, andare not restrictive of the subject matter, as claimed. In thisapplication, the use of the singular includes the plural, the word “a”or “an” means “at least one”, and the use of “or” means “and/or”, unlessspecifically stated otherwise. Furthermore, the use of the term“including”, as well as other forms, such as “includes” and “included”,is not limiting. Also, terms such as “element” or “component” encompassboth elements or components comprising one unit and elements orcomponents that comprise more than one unit unless specifically statedotherwise.

The section headings used herein are for organizational purposes and arenot to be construed as limiting the subject matter described. Alldocuments, or portions of documents, cited in this application,including, but not limited to, patents, patent applications, articles,books, and treatises, are hereby expressly incorporated herein byreference in their entirety for any purpose. In the event that one ormore of the incorporated literature and similar materials defines a termin a manner that contradicts the definition of that term in thisapplication, this application controls.

Current methods and sensors for detecting solvents in variousenvironments have numerous limitations. Such limitations includedetection speed, detection efficiency, detection accuracy, andreproducibility. For instance, current methods of detecting solventswithin solvent feed stocks require sample isolation and chemicalanalysis. Such processes may take several days to complete. Suchprocesses may also require the utilization of sophisticated instruments.

The present disclosure addresses the aforementioned limitations byutilizing various phosphorous-based photoluminescent compounds to detectsolvents. In some embodiments, the present disclosure pertains tomethods of monitoring an environment for the presence of a solvent byutilizing photoluminescent compounds. In some embodiments illustrated inFIG. 1, the methods of the present disclosure include exposing theenvironment to a luminescent compound (step 10), monitoring a change inthe relative luminescence emission intensity of the luminescent compound(step 12), and correlating the observations to the presence or absenceof a solvent in the environment (step 14). In particular, the absence ofa change in the relative luminescence emission intensity of theluminescent compound can indicate the absence of the solvent from theenvironment. Likewise, the presence of a change in the relativeluminescence emission intensity of the luminescent compound can indicatethe presence of the solvent in the environment.

In some embodiments, the present disclosure pertains to sensors formonitoring an environment for the presence of a solvent. The sensors ofthe present disclosure generally include one or more phosphorous-basedluminescent compounds.

As set forth in more detail herein, the methods and sensors of thepresent disclosure can have various embodiments. For instance, themethods and sensors of the present disclosure can utilize various typesof luminescent compounds. In addition, various methods may be utilizedto expose various environments to the luminescent compounds in order todetect various solvents. In addition, a change in the relativeluminescence emission intensity of a luminescent compound can bemonitored in various manners.

Luminescent Compounds

The methods and sensors of the present disclosure may utilize variousluminescent compounds. In some embodiments, the luminescent compoundsinclude a phosphorous atom with one or more carboxyl groups that arecoordinated with one or more metallic ions, such as lanthanide ions,yttrium ions, and combinations thereof.

In some embodiments, the luminescent compounds of the present disclosurealso include one or more light absorbing groups. In some embodiments,the light absorbing groups are coupled to the carboxyl groups. In someembodiments, the light absorbing groups include, without limitation,conjugated groups, aromatic groups, benzene groups, phenyl groups, arylgroups, alkene groups, alkyne groups, azides, cyano groups, andcombinations thereof.

The luminescent compounds of the present disclosure can include varioustypes of metallic ions. For instance, in some embodiments theluminescent compounds of the present disclosure include a singlemetallic ion. In some embodiments, the luminescent compounds of thepresent disclosure include a plurality of the same metallic ions. Insome embodiments, the luminescent compounds of the present disclosureinclude a plurality of different metallic ions. In some embodiments, theluminescent compounds of the present disclosure include a plurality ofmetallic ions at different weight ratios (e.g., weight ratios of 1:1,2:1, 1:3, 3:1, 1:1:1, 2:1:1, 1:2:1, 1:1:2, and the like).

In some embodiments, the luminescent compounds of the present disclosureinclude one or more metallic ions that include, without limitation, La,Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, andcombinations thereof. In some embodiments, the one or more metallic ionsinclude lanthanide ions. In some embodiments, the lanthanide ionsinclude, without limitation, Tb, Eu, Tm, and combinations thereof. Insome embodiments, the luminescent compounds of the present disclosureinclude Tb, Eu, and Tm.

The phosphorous atoms of the luminescent compounds of the presentdisclosure may be in various forms. For instance, in some embodiments,the phosphorous atoms may be in non-oxidized form. In some embodiments,the phosphorous atoms may be oxidized. In some embodiments, thephosphorous atoms may be oxidized by post-synthetic oxidation methods.

The luminescent compounds of the present disclosure may have variousstructures. For instance, in some embodiments, the luminescent compoundsof the present disclosure are porous. In some embodiments, theluminescent compounds of the present disclosure are in the form of acrystalline lattice. In some embodiments, the metallic ions in theluminescent compounds of the present disclosure coordinate with carboxylgroups on adjacent luminescent compounds to form the crystallinelattice.

In some embodiments, the luminescent compounds of the present disclosurehave a honeycomb-like structure. In some embodiments, the luminescentcompounds of the present disclosure are in the form of two-dimensionalhoneycomb sheets. In some embodiments, the luminescent compounds of thepresent disclosure are stacked in an eclipsed arrangement to provide athree-dimensional solid with large hexagonal channels.

The luminescent compounds of the present disclosure can have varioussurface areas. For instance, in some embodiments, the luminescentcompounds of the present disclosure have surface areas that range fromabout 50 m²/g to about 1,000 m²/g. In some embodiments, the luminescentcompounds of the present disclosure have surface areas that range fromabout 250 m²/g to about 800 m²/g. In some embodiments, the luminescentcompounds of the present disclosure have surface areas that range fromabout 500 m²/g to about 750 m²/g. In some embodiments, the luminescentcompounds of the present disclosure have surface areas that range fromabout 500 m²/g to about 600 m²/g.

The luminescent compounds of the present disclosure can have alsovarious quantum yields. For instance, in some embodiments, theluminescent compounds of the present disclosure have absolute quantumyields of photoluminescence (ϕ_(PL)) that range from about 20% to about95%. In some embodiments, the luminescent compounds of the presentdisclosure have ϕ_(PL) values that range from about 35% to about 95%. Insome embodiments, the luminescent compounds of the present disclosurehave ϕ_(PL) values that range from about 50% to about 90%. In someembodiments, the luminescent compounds of the present disclosure haveϕ_(PL) values that range from about 80% to about 90%.

In some embodiments, the luminescent compounds of the present disclosureinclude one or more of compounds 1-9, as presented herein.

In some embodiments, each of M₁, M₂ and M₃ in compounds 1-9 representmetallic ions that include, without limitation, La, Ce, Pr, Nd, Pm, Sm,Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, and combinations thereof. In someembodiments, each of M₁, M₂ and M₃ in compounds 1-9 represent lanthanideions that include, without limitation, Tb, Eu, Tm, and combinationsthereof.

In some embodiments, each of R₁, R₂, R₃, R₅, and R₆ in compounds 1-9include, without limitation, light absorbing groups (as describedpreviously), hydrogen (where feasible), oxygen, carbon-containinggroups, aliphatic groups, non-aromatic groups, conjugated groups,aromatic groups, benzene groups, phenyl groups, aryl groups,heterocycles, cyclic groups, alkyl groups, alkane groups, alkene groups,alkyne groups, halides, azides, cyano groups, methyl groups, nitrogengroups, alkoxyl groups, carboxyl groups, carbonyl groups, ethers,esters, acetyl groups, acetoxy groups, acetomethoxy groups,acetoxymethyl esters, acetoxyalkyl esters, alkoxyalkyl esters, boroncontaining groups, silicon containing groups, phosphorous containinggroups, sulfur containing groups, arsenic containing groups, germaniumcontaining groups, selenium containing groups, aluminum containinggroups, tin containing groups, antimony containing groups, telluriumcontaining groups, lead containing groups, bismuth containing groups,polonium containing groups, cycloamines, heteroatoms, and combinationsthereof.

In some embodiments, each of R₁, R₂ and R₃ in compounds 1-9 includelight absorbing groups. In some embodiments, the light absorbing groupsinclude a phenyl group.

In some embodiments, R₄ in compounds 2, 5 and 8 include, withoutlimitation, O, S, NR₇, CR₈R₉, and combinations thereof. In someembodiments, each of R₇, R₈ and R₉ includes, without limitation, lightabsorbing groups, hydrogen, oxygen, carbon-containing groups, aliphaticgroups, non-aromatic groups, conjugated groups, aromatic groups, benzenegroups, phenyl groups, aryl groups, heterocycles, cyclic groups, alkylgroups, alkane groups, alkene groups, alkyne groups, halides, azides,cyano groups, methyl groups, nitrogen groups, alkoxyl groups, carboxylgroups, carbonyl groups, ethers, esters, acetyl groups, acetoxy groups,acetomethoxy groups, acetoxymethyl esters, acetoxyalkyl esters,alkoxyalkyl esters, boron containing groups, silicon containing groups,phosphorous containing groups, sulfur containing groups, arseniccontaining groups, germanium containing groups, selenium containinggroups, aluminum containing groups, tin containing groups, antimonycontaining groups, tellurium containing groups, lead containing groups,bismuth containing groups, polonium containing groups, cycloamines,heteroatoms, and combinations thereof. In some embodiments, R₄ includesoxygen.

The R₄ group can be appended to the luminescent compounds of the presentdisclosure in various manners. For instance, in some embodiments, the R₄group is appended to the luminescent compound through post-syntheticmodification steps.

In some embodiments, the luminescent compounds of the present disclosureinclude compound 8. In some embodiments, each of R₁, R₂, and R₃ incompound 8 includes phenyl groups. In some embodiments, each of M₁, M₂,and M₃ in compound 8 includes Tb(III). In some embodiments, R₄ includesoxygen that has been appended through post-synthetic oxidation.

In some embodiments, the luminescent compounds of the present disclosureinclude compound 9. In some embodiments, each of R₁, R₂, and R₃ incompound 9 includes phenyl groups. In some embodiments, each of M₁, M₂,and M₃ in compound 9 includes Tb(III). In some embodiments, each of R₅and R₆ in compound 9 includes, without limitation, carbon-containinggroups (e.g., aliphatic or aromatic carbons), hydrogen, and combinationsthereof.

Exposure of Luminescent Compounds to Environments

The luminescent compounds of the present disclosure may be exposed tovarious environments. For instance, in some embodiments, the environmentincludes, without limitation, a liquid environment, a solid environment,a gaseous environment, and combinations thereof.

In some embodiments, the environment is a liquid environment. In someembodiments, the liquid environment includes, without limitation,reservoirs, water formations, solutions, solvent feed stocks, andcombinations thereof.

In some embodiments, the environment includes air. In some embodiments,the environment includes a landfill. In some embodiments, theenvironment is in its native form. In some embodiments, the environmentis a sample (e.g., an aliquot) of its native form.

The luminescent compounds of the present disclosure may be exposed to anenvironment in various manners. For instance, in some embodiments, theexposing occurs by a method that includes, without limitation, mixing,incubating, swapping, dipping, and combinations thereof.

In some embodiments, the exposing occurs by mixing the luminescentcompound with the environment. In some embodiments, the exposing occursby associating the environment with a structure that is embedded with aluminescent compound (e.g., a test strip).

In some embodiments, the luminescent compound is purified beforeexposure to an environment. For instance, in some embodiments, theluminescent compound is heated prior to exposure to an environment. Insome embodiments, the luminescent compound is dried in a vacuum prior toexposure to an environment. In some embodiments, such purification stepsreduce or eliminate the amount of solvents or impurities associated witha luminescent compound.

Solvents to be Detected

The methods of the present disclosure may be utilized to detect varioussolvents from an environment. In some embodiments, the environmentincludes a single solvent. In some embodiments, the environment includesa plurality of different solvents. In some embodiments, the solvent isin the form of at least one of liquids, gases, solids, and combinationsthereof. In some embodiments, the solvent includes, without limitation,organic solvents, inorganic solvents, aqueous solvents, and combinationsthereof. In some embodiments, the solvent to be detected includes,without limitation, water, alcohols, dioxane, toluene, dimethylformamide, hexanes, chloroform, acetonitrile, pyridine, deuterium oxide,and combinations thereof.

Monitoring of Change in Relative Luminescence Emission Intensity

As set forth previously, the relative luminescence emission intensity ofa luminescent compound of the present disclosure changes uponinteraction with a solvent. As such, the absence of a change in therelative luminescence emission intensity of the luminescent compound canindicate the absence of the solvent from the environment. Likewise, thepresence of the change in the relative luminescence emission intensityof the luminescent compound can indicate the presence of the solvent inthe environment.

In some embodiments, the relative luminescence emission intensity of theluminescent compound increases in relation to its original luminescenceemission intensity upon exposure to a solvent. In some embodiments, therelative luminescence emission intensity of the luminescent compounddecreases in relation to its original luminescence emission intensityupon exposure to a solvent.

Without being bound by theory, the change in the relative luminescenceemission intensity of a luminescent compound of the present disclosurecan occur by various mechanisms. For instance, in some embodiments, thechange in the relative luminescence emission intensity of theluminescent compound occurs when the solvent reversibly penetrates theluminescent compound. In some embodiments, the change in the relativeemission intensity of the luminescent compound is caused by relativechanges in intensity of emission from one or more metallic ionsassociated with the luminescent compound. For instance, in someembodiments where the luminescent compound includes two or more metallicions (e.g., two or more lanthanides), the change in the relativeluminescence emission intensity of the luminescent compound can becaused by relative changes in intensity of emission from each metallicion.

In some embodiments, the change in the relative luminescence emissionintensity of the luminescent compound is reversible. For instance, insome embodiments, the change in the relative luminescence emissionintensity of the luminescent compound is reduced or eliminated as thesolvent dissociates from the luminescent compound.

The change in the relative luminescence emission intensity of theluminescent compound can be observed in various manners. For instance,in some embodiments, the change in the relative luminescence emissionintensity of the luminescent compound is represented by a change incolor (e.g., a change in color from yellow to green upon interactionwith a solvent). In some embodiments, the change in the relativeluminescence emission intensity of the luminescent compound isrepresented by a change in visible light emission intensity. In someembodiments, the change in the relative luminescence emission intensityof the luminescent compound is represented by a change in a visiblelight emission pattern.

The change in the relative luminescence emission intensity of theluminescent compound can be monitored in various manners. For instance,in some embodiments, the monitoring occurs visually (e.g., visualobservation of a color change). In some embodiments, the monitoringoccurs in real-time. In some embodiments, the monitoring occurs byutilization of a device, such as a spectrometer.

In some embodiments, a single luminescent compound can be utilized tomonitor the presence of a plurality of different solvents in theenvironment. For instance, in some embodiments, each of the plurality ofdifferent solvents causes a distinguishable change in the relativeluminescence emission intensity of the luminescent compound. In morespecific embodiments, each of the plurality of different solvents causesa distinguishable change in the color of the luminescent compound

In some embodiments, a plurality of different luminescent compounds areutilized to monitor the presence of one or more solvents in theenvironment. For instance, in some embodiments, a solvent causesdistinguishable changes in the relative luminescence emissionintensities of different luminescent compounds.

Sensors

Additional embodiments of the present disclosure pertain to sensors formonitoring an environment for the presence of a solvent. The sensors ofthe present disclosure generally include one or more luminescentcompounds of the present disclosure. Suitable luminescent compounds weredescribed previously.

In some embodiments, the sensors of the present disclosure include asingle luminescent compound. In some embodiments, the single luminescentcompound is capable of monitoring the presence of a plurality ofdifferent solvents in the environment.

In some embodiments, the sensors of the present disclosure include aplurality of different luminescent compounds. In some embodiments, theplurality of different luminescent compounds are capable of monitoringthe presence of one or more solvents in the environment.

The sensors of the present disclosure may be in various forms. Forinstance, in some embodiments, the sensors of the present disclosure maybe in the form of a solid structure (e.g., a test strip), where one ormore luminescent compounds are embedded with the solid structure. Insome embodiments, the sensors of the present disclosure are in the formof a liquid or a solution that contains one or more luminescentcompounds.

Additional Embodiments

Reference will now be made to more specific embodiments of the presentdisclosure and experimental results that provide support for suchembodiments. However, Applicants note that the disclosure herein is forillustrative purposes only and is not intended to limit the scope of theclaimed subject matter in any way.

Example 1. On-Off Luminescence Switching in a Terbium-PhosphineCoordination Material and Luminescence Enhancement by Post-SyntheticOxidation

By way of background, the photoluminescent properties oflanthanide-based materials play an important role in modernlight-emitting devices, optoelectronics, and chemical sensors. Theordered, periodic nature and thermal stability of metal-organicframeworks (MOFs) makes them ideal candidates for the preparation ofluminescent Ln-based materials.

MOFs also offer unique chemical tunability. For instance, the so-calledpost-synthetic modification (PSM) chemistry is of current interest as ameans to broadly functionalize MOFs toward targeted applications. PSMhas already been exploited as a means to install a range of reactivechemical moieties into the pores of MOFs, thus inducing highly specifichost-guest sorption and reactivity.

It is envisioned that PSM of Ln-based MOFs should provide convenientways to directly affect, and potentially optimize, important solid-stateluminescence properties (e.g., emissive quantum yields and lifetimes).Thus far, only a limited number of studies have validated thishypothesis, via the following PSM routes: (i) removal or exchange ofcoordinated solvent molecules; (ii) exchange of metal nodes withsecondary lanthanide ions; and (iii) counter-ion exchange.Unfortunately, these types of PSMs are highly structure-dependent andare therefore not generally applicable. It is also difficult tologically predict a priori whether these PSMs will result in thetargeted enhancement of the solid-state luminescence properties.

Meanwhile, luminescence tuning via the direct chemical PSM of organicgroups in a pre-formed MOF has not been successfully demonstrated priorto this Example. This approach is of interest because chemicalmodification of organic chromophores is known to significantly alter theenergy of their triplet excited states, in a predictable manner. This inturn affects the efficacy of the ligand-to-metal energy transfer process(also known as the antenna effect) and thus the metal-basedluminescence.

Applicants have recently addressed ways to construct MOF-type materialsusing substituted triaryl phosphines. The Phosphine CoordinationMaterials (PCMs) are a unique subset of MOFs, characterized by havingpores that are decorated with abundant Lewis basic R₃P: sites.

In this Example, Applicants demonstrate the on-off luminescenceswitching in a terbium-phosphine coordination material 22 (PCM-22) andluminescence enhancement by post-synthetic oxidation of PCM-22. PCM-22is a Tb(III)/triphenylphosphine-based network coordination material. Thematerial has a highly porous honeycomb-like structure with infinitehexagonal 1-D channels. It displays rapid and reversibly switchableon-off luminescence in the solid-state, in response to the presence ofsolvent. Post-synthetic oxidation of the free phosphine sites in PCM-22proceeds quantitatively and in a single-crystal-to-single-crystaltransformation, resulting in significant enhancement of the luminescencequantum yield via optimization of ligand-to-metal energy transfer.

In this Example, Applicants also describe the synthesis of PCM-22, whichwas obtained by the direct reaction of Tb(NO₃)₃ hydrate withtris(p-carboxylato)triphenylphosphine (P(C₆H₄-4-CO2H)₃; tctpH₃). Thedeprotonated trianion tctp³⁻ reacts in a 1:1 fashion with Tb³⁺ cationsto give a charge-neutral and highly symmetric polymer based on thesimple formula unit [Tb(tctp)(OH₂)₃]-3(1,4-dioxane).

PCM-22 displays puckered 2D honeycomb sheets that stack in an eclipsedarrangement to give a 3-D solid with large hexagonal channels (FIG. 2A,FIG. 2B, FIG. 2C, FIG. 2D, and FIG. 2E). The Tb³+ center in PCM-22 has acoordination number of 9, comprised of three facial bis(chelating)carboxylates, and three fac-OH₂ ligands (FIG. 2A). Alternating3-connected phosphine-P and Tb³⁺ nodes give rise to infinite puckeredsheets of fused hexagonal rings with chair conformations (FIG. 2B andFIG. 2C). The resulting 3,3-connected lattice topology is the same asthat exhibited by the pure metallic phases of the heavier group XVelements, As and Sb (FIG. 2D).

PCM-22 inhabits the rarely observed polar space group P3c1. Thus,opposite faces of each sheet are chemically distinct (being comprised ofeither Tb or P atoms). In addition, the individual sheets of PCM-22 areinherently chiral (adjacent sheets consist of the other enantiomer).

The eclipsed close stacking of sheets observed in PCM-22 (FIG. 2C andFIG. 2D) is similar to that observed for many covalent organicframeworks (COFs), where inter-layer n-n interactions dominate thesupramolecular organization. Such stacking of 2-D sheets to give orderedpseudo-3-D materials is propitious because it results in large pores.Eclipsed packing is, however, quite unusual amongst 2-D MOFs, which morecommonly adopt staggered-layer conformations that results in small voidspaces.

In fact, Applicants have observed the latter type of packing in threepreviously reported Zn²⁺-based PCMs constructed using the same tctp³⁻ligand, which exhibit similar 3,3-c hexagonal nets. Interestingly, inthis instance, eclipsing is imposed due to a network of close-rangeinter-layer hydrogen-bonding interactions between Tb-bound OH₂ ligandsand carboxylate-O atoms (FIG. 2E).

The shortest O—O contact distances are 2.74 A. As a result, adjacentsheets are densely packed and the Tb—Tb inter-layer distance is only5.77 A (FIG. 2C). The tctp ligands do not exhibit n-n interactions,since P-aryl groups in alternating layers are not aligned in parallel.The hexagonal channels in PCM-22 have a maximum van der Waals accessibleopening of 14.5 A.

Well-ordered 1,4-dioxane solvent molecules present in the channels ofthe as-synthesized material were easily removed by evacuation at 75° C.,resulting in a BET surface area of 559 m² g⁻¹ (CO₂, 196 K; FIG. 3). Theactivation conditions employed in this work were determined bymonitoring the apparent change in BET surface area as a function ofevacuation temperature (FIG. 3 and FIG. 4).

Crystalline samples were found to suffer a 39% reduction in surface areabetween 75 and 150° C. The measured surface area then remained constantfor all activation temperatures up to 300° C. Thermogravimetric analysis(TGA) confirmed optimal thermal stability with the onset of frameworkdecomposition occurring ca. 450° C. (FIG. 5).

An initial 29.5% mass loss below 100° C. corresponded to the loss of allunbound 1,4-dioxane present in the channels (expected 30.4%), which wasfollowed by a further distinct 3.7% mass loss between 100-190° C.,attributed to the loss of a single coordinated H₂O molecule per Tb(III)(expected 3.1%). Above this temperature, no further mass loss occurreduntil 500° C.

The solid-state luminescence properties of an as-synthesized sample ofPCM-22 were measured at room temperature without pretreatment, resultingin a spectrum characteristic of Tb(III) emission with well-resolvedelectronic transitions at 491, 544, 584 624 and 648 nm due to radiativerelaxation from the ⁵D₄ excited state to the ⁷F_(J) ground state (J=6,5, 4, 3 and 2, respectively; FIG. 6). The average absolute quantum yieldof photoluminescence (ϕ_(PL)) by PCM-22 was 57±3%. PreviousTb(III)-based MOFs have reported ϕ_(PL) in the range of 22-90%.

In PCM-22, there is an extensive H-bonding network. Each metal iscoordinated by three H₂O molecules and the structure also contains asolvent (1,4-dioxane & H₂O) in the channels, all of which are knownemission quenchers (FIG. 2E and FIG. 7). The relatively high ϕ_(PL) ofPCM-22 was therefore surprising.

The number of H₂O molecules present within the quenching sphere of theemissive Ln(III) ion (q) can be approximated by comparison of theemissive lifetime with that of an isostructural material prepared withD₂O ligands. For PCM-22, this yielded an estimated 3.4±0.5 H₂O moleculesper Tb(III) ion, in close agreement with other characterizing data. Thequenching ability of coordinated ligands, such as H₂O, is known todecrease when hydrogen-bonding interactions perturb the normalvibrational frequency of the oscillators that are responsible forcoupling to a lanthanide excited state, resulting in non-radiative decay(e.g., O—H bonds in the case of H₂O).

Without being bound by theory, the accepted indirect excitationmechanism responsible for Tb-centered emission in MOF materials is vialigand-to-metal energy transfer, in which the organic scaffold isinitially photo-excited, which ultimately results in population ofligand-centered triplet (T) excited states via established intersystemcrossing pathways. To optimize lanthanide-based luminescence, it istherefore important to maximize the ligand-to-metal energy transferefficiency. This is achieved by choosing organic chromophores, whose T1energy levels are ca. 2,000-4,000 cm⁻¹ above the excited state of thecorresponding lanthanide ion (20,366 cm⁻¹ for Tb(III)). Examination ofthe phosphorescence spectrum of the free ligand, tctpH₃, dissolved in afrozen glass of 2-methyltetrahydrofuran at 77 K, gave T₁=24,390 cm⁻¹.The T₁ energy of the tctp³⁻ ligand shifts slightly when embedded in thematerial. The isostructural Gd(III)-based version of PCM-22 yielded aT₁=25,253 cm⁻¹ at 77 K.

From earlier work, it was already known that the T1 level of thephosphine oxide derivative of the ligand (P(═O)(C₆H₄-4-CO₂H)₃; tctpoH₃)was 10% higher in energy than the free phosphine, at 26,882 cm⁻¹.Applicants were interested to explore the possibility of furtherenhancement of the Tb(III) emission quantum yield in PCM-22 by using theoxidized ligand to prepare an isostructural material, O=PCM-22.Unfortunately, it is not possible to prepare this material directlyusing the pre-oxidized tctpoH₃ ligand because the P═O moiety formsdirect P=O{circumflex over ( )}Tb bonds, resulting in a completelydifferent material that has been described previously. However,Applicants unexpectantly observed that crystalline PCM-22 samples couldbe easily post-synthetically oxidized by simple, direct treatment withH₂O₂.

The oxidation proceeded quantitatively as monitored by MAS-³¹P{¹H}-NMR,FT-IR and TGA studies (FIG. 5, FIG. 8A, FIG. 8B, and FIG. 9). Mostnotably, the PSM occurred in a single-crystal-to-single-crystal manner,which allowed for the collection of high-quality single crystal X-raydiffraction data (FIG. 10). The oxide P═O distance (1.39 Å) lies withinthe expected range. The X-ray structure also confirmed retention of theoriginal bulk lattice structure and H-bonding network, and that therewas no exfoliation caused by the PSM. The inter-layer Tb—Tb distance inO=PCM-22 (5.81 Å) is almost the same as that observed in the originalPCM-22 structure (5.77 Å).

The isostructural nature of the two materials and the retention of bulkcrystallinity of the functionalized material were confirmed by PXRD(FIG. 11). The measured bulk surface area of O=PCM-22 (346 m² g⁻¹; CO₂,196 K) was slightly diminished compared to PCM-22, but is indicative ofretention of microporosity (FIG. 12). Applicants believe this is thefirst time such a PSM has been fully structurally characterized in aMOF-type material.

Compared to the unoxidized parent material, the average ϕ_(PL) ofO=PCM-22 was substantially increased by 27% to 84±3%, under identicalconditions (FIG. 13). This result clearly demonstrates that Applicantswere able to significantly enhance ligand-to-metal energy transfer inthe solid-state by optimization of the ligand T₁ energy, via a simpleand convenient oxidative PSM. The increase in the observed ϕ_(PL) isconsistent with the trend described by prior work that studied a familyof TbLx complexes and found that ligands, ‘L’, with T1 states>25,000cm⁻¹ resulted in higher quantum yields.

Further investigations into the photoluminescence behavior of PCM-22 andO=PCM-22 revealed that both materials display highly reversible on-offluminescence in response to the degree of solvation. In order toaccurately assess the relationship between the presence of solvents andcoordinated H₂O ligands versus relative luminescence intensity, sampleswere desolvated in situ using a custom-made quartz tube.Counterintuitively, when samples were activated under vacuum at 100° C.over 12 hours, the solid-state luminescence was dramatically diminished.Moreover, temperature-dependent PXRD analysis indicated loss of bulkcrystallinity (FIG. 14A, FIG. 14B, and FIG. 15). In addition,temperature-dependent FT-IR spectroscopy showed a decrease in theintensity of stretching bands attributed to coordinated H₂O above 80° C.(ca. 3400 cm⁻¹; FIG. 16). Exposure of an activated sample to D₂Oresulted in an emissive lifetime change corresponding to the loss of oneH₂O ligand per Tb(III). All of these observations are in directagreement with the TGA studies.

Luminescence quenching as a direct consequence of desolvation has beenobserved in other MOFs. Loss of site-symmetry of individual Tbcoordination environments, as well as changes in inter-layer Tb—Tbdistances, are likely to result in more non-radiative processes.Through-space metal-to-metal energy migration is only favorable betweenions separated by <10 A. Since the intra-layer Tb—Tb separation distancein PCM-22 is 13.7 A, it is clear that inter-layer energy migration mustdominate. Without being bound by theory, it is reasonable to assume thatdesolvation of PCM-22 and O=PCM-22 disrupts the originally well-orderedH-bonding network, resulting in more molecular motions within thematerials and more non-radiative decay pathways.

When the activated materials were re-exposed to a range of solvents(H₂O, alcohols, N,N-dimethylformamide, acetonitrile) either as liquidsor vapors, the luminescence intensity was rapidly recovered. PXRDstudies showed that bulk crystallinity was also quickly restored (FIG.14A). Both the emissive quantum yields and crystallinity were maintainedafter 10 days of standing in solvent (FIG. 14B). The materials appear todisplay ‘soft crystalline’ behavior in that solid-state structuralreorganization is possible without loss of long-range order.

To rule out the alternative possibility that the observed emissionrecovery upon resolvation could be due to physical dissolution andrecrystallization, a sample of desolvated PCM-22 was immersed in solventand constantly monitored over a period of 15 days under an opticalmicroscope equipped with CCD camera. The macroscopic shape and volume ofthe crystals remained unchanged during this time and there was noevidence of nucleation of new crystallites (FIG. 17A, FIG. 17B, FIG.17C, and FIG. 17D).

Next, Applicants decided to test the temporal response limit andreversibility of the materials, as potential visual turn-on sensors forsolvent vapor. Desolvated samples of PCM-22 and O=PCM-22 (vac., 12 h at100° C.) were exposed to fresh solvent (1:1:1 DMF/dioxane/H₂O) withcontinual monitoring of the emission intensity. This revealed that theemission was turned-on in a matter of seconds for both PCM-22 andO=PCM-22 (FIG. 18). After 5 seconds, 65 and 85% of the original emissionintensity had been recovered, while the intensities were 91% and 94%recovered after 5 minutes (for PCM-22 and O=PCM-22, respectively). Theemission intensities reached stable maxima after approximately 60minutes. The samples were easily recycled by reactivation in vacuo andsubsequent exposure to fresh solvent, without any marked loss ofemission intensity or response time (FIG. 18).

The measured emissive lifetimes (FIG. 18, insets) demonstrate therecovery of Tb(III) emission was independent of changing surfacecharacteristics of the crystalline powders upon activation andresolvation. Lifetimes are commonly used to demonstrate efficiency oflanthanide emission. The first activation showed a large difference infresh samples of PCM-22 and O=PCM-22, the latter being more efficient.Upon exposure to solvent, the lifetimes increased, which is indicativeof a decrease in the number of radiative decay pathways.

In summary, Applicants have shown that a new Tb(III)-based PhosphineCoordination Material with 2-D hexagonal honeycomb like structure showsreversible luminescence intensity changes in direct response to theextent of solvation. The most emissive state corresponds to the mostsolvated state, in which long-range structural order is maximized.Targeted oxidation of R₃P: sites in PCM-22 was also demonstrated as asimple and convenient means to post-synthetically enhance thesolid-state O_(PL) via tuning of the T state of the organic frameworkcomponents.

Example 1.1. Materials and Methods

Tris(p-carboxylated) triphenylphosphine, P(C₆H₄-4-COOH)₃ was synthesizedaccording to a literature method (Humphrey et al., Dalton Trans., 2009,2298). 1,4-dibromobenzene (99%; Acros), n-butyllithium (2.5 M inhexanes; Acros) and metal salts (Sigma-Aldrich) were used as received.All solvents (Fisher Scientific) were pre-dried and degassed using anInnovative Technologies Solvent Purification System. FT-IR data werecollected using a Thermo Scientific Nicolet iS50 spectrometer equippedwith an ATR apparatus. TGA analyses were performed on a TA InstrumentsQ50 analyzer using high purity N₂ carrier gas in the range of 25-800° C.Solid-state NMR data were collected on a Bruker Avance-400 spectrometer(400 MHz for ¹H) equipped with a standard 4 mm MAS NMR probe head.Spinning rates varied between 6 and 12 kHz. H₃PO₄ was used as anexternal reference for chemical shift calculations. Powder X-raydiffraction (PXRD) experiments were performed in borosilicatecapillaries in a Rigaku R-Axis Spider diffractometer using Cu-Kαradiation with data collected in the range 5-40° 2θ. Simulated PXRD wasgenerated using single crystal reflection data via SimPowPatt facilityin PLATON. All samples were activated under reduced pressure at variabletemperatures prior to gas uptake experiments. Gas adsorption isothermswere recorded on a Quantachrome Autosorb-1 system. All gases (99.995+%)were purchased from Praxair. Photophysical measurements were recorded ona Photon Technology International QM 4 spectrophotometer equipped with a6-inch diameter K Sphere-B integrating sphere.

Example 1.2. Synthesis of PCM-22

The phosphine ligand P(C₆H₄-4-COOH)₃ (39 mg, 0.10 mmol) was dissolved indmf/H₂O/dioxane (1:1:1, 4.0 cm³), which had been degassed by bubbling N₂for at least 10 minutes. To this was added a second solution of Tb(NO₃)₃hydrate (0.20 mmol; two equivalents) dissolved in 4.0 cm³ of the samesolvent. The reaction was heated in a scintillation vial using agraphite thermal bath at 80° C. for 3-4 days. The resulting colorlessrod-like crystals of PCM-22 were isolated by washing and decanting anyimpurities away using the degassed DMF/H₂O/dioxane solvent mixture.

The solid was then Buchner filtered and thoroughly washed with the samesolvent mixture. The crystalline solid was allowed to air dry and thenstored under an N₂ atmosphere. Yield=25%; Anal. Found: C, 45.2; H, 2.66;P, 5.19%. C₂₁H₁₂TbO₆P requires: C, 45.5; H, 2.20; P, 5.63%. Vim,(solid): 374 s, 486 m, 531 w, 539 w, 577 w, 612 m, 618 w, 662 w, 677 w,699 w, 727 s, 773 s, 861 s, 876 m, 969 w, 1015 m, 1045 w, 1080 w, 1116s, 1133 w, 1180 w, 1213 w, 1254 m, 1287 w, 1327 w, 1397 br s, 1494 w,1523 s, 1578 s, 1653 m, 2851 w, 2886 w, 2912 w, 2953 w, 3243 br m.

Example 1.3. Synthesis of O=PCM-22

An aliquot of hydrogen peroxide (0.5 mmol, 30%) was added directly intothe mother liquor of the freshly synthesized PCM-22. The reaction wasleft to stand in the synthesis vial, at room temperature withoutstirring. This process was repeated three more times with fresh reagent.The solution mixture (which turned cloudy white upon addition of theperoxide) was decanted away and the remaining crystals washed with freshaliquots of DMF/H₂O/dioxane solvent. O=PCM-22 crystals remainedidentical to those of the parent material and were suitable for singlecrystal X-ray analysis. The crystals were isolated by Buchner filtrationand washed with abundant DMF/H₂O/dioxane mixture. Yield=90%; Anal.Found: C, 44.2; H, 3.22; P, 5.12%. C₂₁H₁₂TbO₇P requires: C, 44.55; H,2.14; P, 5.47%. V_(max) (solid): 419 w, 486 m, 531 w, 578 m, 612 m, 617w, 660 w, 675 w, 698 w, 728 s, 772 s, 860 s, 889 m, 969 w, 1015 m, 1043w, 1080 w, 1114 s, 1133 w, 1180 br m, 1253 m, 1287 w, 1288 w, 1390 br s,1495 w, 1523 s, 1581 s, 1651 s, 2851 w, 2886 w, 2915 w, 2953 w, 3256 brm.

Example 1.4. Analysis

The solid-state NMR ³¹P{¹H} NMR (162 MHz) spectra of PCM-22 and O=PCM-22were recorded by Hahn-echo spin-mapping experiments, varying the carrierfrequency from +1000 to −1000 ppm. All spectra were collected using astandard 4 mm NMR probe, a 4 mm ZrO₂ rotor with spinning rates between10 and 13 kHz and 3.5 qs(180°) and 7 qs(90°) pulses. The ³¹P{¹H} NMRspectrum for static Tb-PCM-22 showed one broad, symmetrical peakcentered at 0 ppm with line width of 92 kHz (FIG. 8A). The signal shapedid not change with spinning rate (10-12 kHz). Such a wide signal andlack of paramagnetic (Fermi-contact) shifts can be attributed to directelectron-nucleus dipolar interactions and a short relaxation time. It isprobable that this signal belongs to remote phosphorous atoms while thenuclei closely located to paramagnetic ions were not observable due toan extremely short relaxation time. The ³¹P{¹H} NMR spectrum for staticO=PCM-22 was obtained by spin-mapping at various carrier frequencies.The spectrum (FIG. 8B) showed two peaks at 0 and −1000 ppm, the shape ofwhich correspond to an axially-symmetric chemical shift tensor. Theisotropic chemical shift 5(iso) can be estimated as −330 ppm. However,the spinning sample showed an isotropic shift of +32.7 ppm. Therefore,the spectra showed two phosphorous peaks with values of +32.7 and −1000ppm belonging to separate, but closely located ³¹P nuclei.

Example 1.5. Photophysical Measurement

For quantum yield measurements, an integrating sphere was used. Quantumyield was calculated by dividing the area under the emission peaks ofthe complex by the difference between the area under the excitation peakof the sample from that of a blank (BaSO₄).

(Aem(sample)/(Aex(blank)−Aex(sample)), where A=area under peak).

Neglecting other quenchers, it is possible to get a general value of thewater molecules (q) attached to the inner sphere of the ion. The qvalue, or hydration state, was determined based on equation [1] and thelifetime measurements obtained for PCM22/H₂O and PCM22/D₂O by monitoringthe emission peak value at 543 nm, using an excitation of 340 nm. A wasfound to be 2.1 ms⁻¹ for Tb⁺³ and a given error of ±0.5 H₂O molecules.As synthesized, the value of q was about 3H₂O (supported by X-raydiffraction). Upon activation and resolvation with D₂O, q was about2H₂O, implying that a single H₂O had been removed and then replaced byD₂O (supported by TGA).

q-A(k _(H2o) ,k _(D2o))  [1]

As Synthesized q=3.4±0.5 water molecules-2.1 ms¹ (0.583 ms-1.022 ms).Resolvation with D₂O eq: 2.4±0.5_(water molecules-2.1) ms″¹(0.692_(ms)-1.097 ms).

Example 2. Observation of Color Changes in Phosphine CoordinationMaterials Upon Exposure to Solvents

In this Example, PCM-22 was prepared using the pure Ln elements Eu andTb. The former Eu version emits red light, and the latter Tb versionemits green light. When Applicants prepared isostructural materials withvarying amounts of both metals in the same material, the net effect wasto mix the colors (engendering yellow light, as illustrated in FIG.19A). Next, when the material was evacuated, the luminescence turned off(i.e., the crystals became non-luminescent). However, upon exposure to arange of different liquid solvents or vapors thereof, the luminescenceswitched back on instantaneously (FIG. 19B). The color of the materialranged from green to yellow or orange or deep red, depending on the typeof solvent (FIG. 19B).

The same detection mechanism can be applied to study the amounts of animpurity solvent within another solvent. For instance, Applicants candetect the presence of water in another solvent, depending on how muchgreen light was present in the emission. The visually striking effect isalso observed for PCM-22 version using different combinations of Lnmetals. For instance, when applicants mixed a third metal (such as Tm)into PCM-22, Applicants accessed blue-to-white color transitions (FIG.19C).

Without further elaboration, it is believed that one skilled in the artcan, using the description herein, utilize the present disclosure to itsfullest extent. The embodiments described herein are to be construed asillustrative and not as constraining the remainder of the disclosure inany way whatsoever. While the embodiments have been shown and described,many variations and modifications thereof can be made by one skilled inthe art without departing from the spirit and teachings of theinvention. Accordingly, the scope of protection is not limited by thedescription set out above, but is only limited by the claims, includingall equivalents of the subject matter of the claims. The disclosures ofall patents, patent applications and publications cited herein arehereby incorporated herein by reference, to the extent that they provideprocedural or other details consistent with and supplementary to thoseset forth herein.

What is claimed is:
 1. A method of monitoring an environment for apresence of a solvent comprising: exposing a luminescent compound to theenvironment, wherein a relative luminescence emission intensity of theluminescent compound changes upon interaction with the solvent; andmonitoring a change in the relative luminescence emission intensity ofthe luminescent compound, wherein the luminescent compound includescompounds comprising formula (8):

Formula (8) wherein M₁ is one ion of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,Dy, Ho, Er, Tm, Yb, Lu, or Y; wherein M₂ is one ion of La, Ce, Pr, Nd,Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, or Y; wherein M₃ is one ionof La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, or Y;wherein R₁ is a conjugated group, an aromatic group, a phenylene group,an aryl group, a heterocycle, or a cyclic group; wherein R₂ is aconjugated group, an aromatic group, a phenylene group, an aryl group, aheterocycle, or a cyclic group; wherein R₃ is a conjugated group, anaromatic group, a phenylene group, an aryl group, a heterocycle, or acyclic group; wherein R₄ is O or S; wherein M₁ and M₂ are the same or M₁and M₂ are different; wherein M₂ and M₃ are the same or M₂ and M₃ aredifferent; wherein M₁ and M₃ are the same or M₁ and M₃ are different;wherein the compounds of formula (8) in the crystalline lattice arecoordinated through one or more of M₁, M₂, or M₃.
 2. The method of claim1, wherein the environment is selected from the group consisting of aliquid environment, a solid environment, a gaseous environment, andcombinations thereof.
 3. The method of claim 2, wherein the liquidenvironment is selected from the group consisting of reservoirs, waterformations, solutions, solvent feed stocks, and combinations thereof. 4.The method of claim 1, wherein environment comprises air or a landfill.5. The method of claim 1, wherein the environment comprises a singlesolvent or a plurality of different solvents, and wherein the solvent isselected from the group consisting of organic solvents, inorganicsolvents, aqueous solvents, and combinations thereof.
 6. The method ofclaim 1, wherein the environment comprises a single solvent or aplurality of different solvents, and wherein the solvent is selectedfrom the group consisting of acetonitrile, alcohols, amines, benzenes,chloroform, deuterium oxide, dichloromethane, dimethyl formamide,dimethyl sulfoxide, dioxanes, ethers, esters, glycerin, glycols,hexanes, ketones, pyridines, sulfides, thiols, thiophenes, toluenes, andcombinations thereof.
 7. The method of claim 1, wherein the exposingoccurs by a method selected from the group consisting of mixing,incubating, swapping, dipping, and combinations thereof; or wherein theexposing occurs by mixing the luminescent compound with the environment;or wherein the exposing comprises associating the environment with astructure embedded with the luminescent compound.
 8. The method of claim1, wherein the change in the relative luminescence emission intensity ofthe luminescent compound is reversible.
 9. The method of claim 1,wherein the change in the relative luminescence emission intensity ofthe luminescent compound is represented by a change in color; or whereinthe change in the relative luminescence emission intensity of theluminescent compound is represented by a change in visible lightemission intensity; or wherein the change in the relative luminescenceemission intensity of the luminescent compound is represented by achange in visible light emission pattern.
 10. The method of claim 1,wherein the monitoring occurs visually; or wherein the monitoring occursin real-time; wherein the monitoring occurs by utilization of aspectrometer; or wherein a single luminescent compound is utilized tomonitor the presence of a plurality of different solvents in theenvironment.
 11. The method of claim 1, wherein M₁ is one of La³⁺, Ce³⁺,Pr³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tb³⁺, Yb³⁺, Lu³⁺, orY³⁺; wherein M₂ is one of La³⁺, Ce³⁺, Pr³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺,Dy³⁺, Ho³⁺, Er³⁺, Tb³⁺, Yb³⁺, Lu³⁺, or Y³⁺; wherein M₃ is one of La³⁺,Ce³⁺, Pr³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺, Dy³⁺, Ho³⁺, Er³⁺, Tb³⁺, Yb³⁺, Lu³⁺,or Y³⁺.
 12. The method of claim 1, wherein M₁ and M₂ are the same, or M₂and M₃ are the same, or M₁ or M₃ are the same, or M₁, M₂, and M₃ are thesame.
 13. The method of claim 1, wherein M₁ is one ion of Tb, Eu, or Gd;wherein M₂ is one ion of Tb, Eu, or Gd; and wherein M₃ is one ion of Tb,Eu, or Gd.
 14. The method of claim 1, wherein R₁ is phenylene, R₂ isphenylene, and R₃ is phenylene.
 15. The method of claim 1, wherein thecrystalline lattice is porous.